Array relations broken since 3.26 with MongoDB

Does anybody face similar issues like this:

Only plain objects can be passed to Client Components from Server Components. Objects with toJSON methods are not supported. Convert it manually to a simple value before passing it to props.
  {createdAt: ..., updatedAt: ..., roles: ..., email: ..., id: {buffer: ...}, loginAttempts: ..., collection: ..., _strategy: ...}

Our template worked fine until I upgraded to 3.25 (problem does still exist with 3.28). I can't really get the root-cause, but it happends in the moment that I'm adding "roles" to "users":

{
      name: 'roles',
      type: 'relationship',
      relationTo: 'roles',
      hasMany: true,
      required: false,
      saveToJWT: true,
      access: {
        create: () => true,
        update: isAdminFieldLevel,
        read: () => true,
      },
      admin: {
        position: 'sidebar',
        hidden: false,
        description: {
          en: 'User roles. Admin has full access. Editor is the most common role, with limited access. First user is always admin.',
          de: 'Benutzerrollen. Admin hat vollständigen Zugriff. Editor ist der allgemeine Benutzer, mit begrenztem Zugriff. Erster Benutzer ist immer Admin.',
        },
      },
    },

so it seems that payload is having issues with relationship fields in MongoDB. There have to be other people facing this issue as well.. I'm trying to analyse it better now and comparing the behaviour before the upgrade with the behaviour now and will update this threat.

this PR feels like the problematic one:

seems like I can narrow it down to this hook:

 hooks: {
    beforeValidate: [
      async ({ req, data = {}, operation }) => {
        if (operation === 'create') {
          try {
            const { totalDocs } = await req.payload.find({
              collection: 'users',
              limit: 0,
            })

            // Determine which role to assign. First user should be admin
            const isAdmin =
              totalDocs === 0 ||
              (data.email &&
                process.env.ALLOWED_EMAIL_DOMAINS?.split(',').includes(data.email.split('@')[1]))

            // Find the appropriate role
            const role = await findRole(req.payload, isAdmin ? 'admin' : 'editor')

            console.log("data", data)

            if (role?.id) {
              req.payload.logger.info(`Assigning ${role.name}, id: ${role.id} role to new user`)
              return {
                ...data,
                roles: [role.id],
              }
            } else {
              req.payload.logger.error('No suitable role found for user')
            }
          } catch (error) {
            req.payload.logger.error(`Error in beforeValidate hook: ${error}`)
          }
        }
        return data
      },
    ],
  },

setting a relation doesn't seem to work any longer in this hook

Issue is, that Payload - when using the hook in this case - is writing an ObjectId in the relation field in the DB, where it does later expect a string.. that has changed.